JP2002367676A - Manufacturing method of solid electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a solid electrolyte battery in which unevenness of battery capacity is prevented and quality is stabilized. SOLUTION: The manufacturing method comprises an assembly process, in which a battery precursor that is made by packing a positive electrode and a negative electrode capable of storing and releasing lithium and a solid electrolyte in a film-shape outer case is manufactured, and an initial charging process, in which the above battery precursor is charged initially in an environmental temperature in the range 15 deg.C or more and 50 deg.C or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a solid electrolyte battery having a positive electrode and a negative electrode capable of inserting and extracting lithium, and a non-aqueous electrolyte.

[0002]

2. Description of the Related Art In recent years, camera-integrated VTRs, mobile phones,
Many portable electronic devices such as laptop computers have appeared, and their size and weight have been reduced. Research and development for improving the energy density of batteries, especially secondary batteries, as portable power sources for these electronic devices are being actively promoted. In particular, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are expected to have a higher energy density than conventional aqueous electrolyte secondary batteries, such as lead batteries and nickel cadmium batteries.

[0003]

Incidentally, when manufacturing a non-aqueous electrolyte battery, that is, a so-called solid electrolyte battery, which comprises an electrolyte salt, a gel electrolyte composed of a non-aqueous solvent, and a matrix polymer as an electrolyte, a positive electrode and a negative electrode are used. After the battery was assembled by packaging the solid electrolyte with a film-like packaging case or the like, the battery was charged for the first time at room temperature.

[0004] However, when first charging at room temperature,
In some cases, the battery capacity varied, and it was not easy to manufacture a solid electrolyte battery having stable quality.

Accordingly, the present invention has been proposed in view of the above-mentioned conventional circumstances, and has as its object to provide a method for manufacturing a solid electrolyte battery in which a variation in battery capacity is prevented and a solid electrolyte battery having stable quality is manufactured. It is a thing.

[0006]

Means for Solving the Problems As a result of diligent studies conducted by the present inventors to achieve the above object, the discharge capacity of a solid electrolyte battery depends on the environmental temperature at the time of initial charging. It has been found that controlling the environmental temperature during charging to a certain range can prevent variations in battery capacity.

The present invention has been completed on the basis of such findings, and is an assembly for producing a battery precursor in which a positive electrode and a negative electrode capable of inserting and extracting lithium and a solid electrolyte are packaged in a film-shaped package case. And an initial charging step of performing an initial charging of the battery precursor in an environment temperature range of 15 ° C. or more and 50 ° C. or less.

[0008] Originally, the ambient temperature at the time of the first charging was room temperature. However, the room temperature varies depending on the season, time, weather, and the like, and is not constant. For this reason, the solid electrolyte battery initially charged at room temperature has a variation in battery capacity according to the change in room temperature.

On the other hand, according to the method for manufacturing a solid electrolyte battery according to the present invention, since the temperature environment at the time of the first charge is controlled within a certain range, the variation in the battery capacity after the first charge is prevented. Therefore, according to the method for manufacturing a solid electrolyte battery according to the present invention, a solid electrolyte battery having stable quality can be manufactured.

In the method for producing a solid electrolyte battery according to the present invention, in particular, in the first charging step, the first charging of the battery precursor is performed at an ambient temperature of 30 ° C. or more and 50 ° C. or less. It is appropriate to carry out the
It is optimal to perform the first charging within a range of 0 ° C. or more and 35 ° C. or less.

[0011] The first charging is performed by setting the temperature environment at the time of the first charging to an environment temperature range of 30 ° C or higher and 50 ° C or lower, more preferably a temperature range of 30 ° C or higher and 35 ° C or lower. The subsequent variation in battery capacity is prevented, and the internal resistance of the solid electrolyte is further reduced, so that the discharge capacity per cycle is increased. Therefore, a solid electrolyte battery having a high capacity and stable quality can be manufactured.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a solid electrolyte secondary battery to which the present invention is applied will be described in detail with reference to the drawings.

A solid electrolyte secondary battery 1 to which the present invention is applied
Is a so-called lithium ion secondary battery including a solid electrolyte or a gel electrolyte, and as shown in FIGS. 1 and 2, between a positive electrode active material layer and a negative electrode active material layer. A battery element 2 provided with a solid electrolyte or a gel electrolyte is accommodated in a layered film-shaped outer case 3 and is sealed by heat welding the periphery.

The battery element 2 has a positive terminal lead 4 electrically connected to the positive electrode constituting the battery element 2 and a negative terminal lead 5 electrically connected to the negative electrode. The terminal lead 4 and the negative electrode terminal 5
It is drawn out of the film-shaped outer case 3.

As the solid electrolyte, for example, an inorganic electrolyte, a polymer electrolyte or a gel electrolyte obtained by mixing and dissolving an electrolyte in a polymer compound is used. The gel electrolyte is
It is composed of a plasticizer containing a lithium salt and 2 to 30% by weight of a matrix polymer. At this time, esters, ethers, carbonates and the like can be used alone or as one component of a plasticizer.

Examples of the polymer material used for the gel electrolyte battery include silicon gel, acrylic gel, acrylonitrile gel, modified polyphosphazene polymer, polyethylene oxide, polypropylene oxide, and composite polymers, crosslinked polymers and modified polymers thereof. Examples of the fluorine-based polymer include poly (vinylidene fluoride) and poly (vinylidene fluoride)
-co-hexafluoropropylene), poly (vinylidene fluoride-co-tetrafluoroethylene), poly (vinylidene fluoride-co-trifluoroethylene), and the like, and various mixtures thereof can be used. Among these polymer materials, it is particularly preferable to use a fluorine-based polymer such as poly (vinylidene fluoride) or poly (vinylidene fluoride-co-hexafluoropropylene) from the viewpoint of oxidation-reduction stability.

As the lithium salt to be contained in the gel electrolyte, a lithium salt used in a usual battery electrolyte can be used. Examples thereof include the following, but are not limited thereto.

For example, lithium chloride lithium bromide, lithium iodide, lithium chlorate, lithium perchlorate, lithium bromate, lithium iodate, lithium nitrate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium acetate, bisulfate Lithium (trifluoromethanesulfonyl) imide, LiAsF ₆ , LiCF ₃ S
O ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiAlCl ₄ , L
iSiF _{6 and the} like can be mentioned.

These lithium compounds may be used alone or as a mixture of a plurality of them.
F ₆ and LiBF ₄ are desirable from the viewpoint of oxidation stability.

As for the concentration of the lithium salt to be dissolved, a gel electrolyte can be used in a plasticizer at a concentration of 0.1 to 3.0 mol, preferably 0.5 to 2.0 mol / l. .

A solid electrolyte secondary battery 1 to which the present invention is applied
Other than using a gel electrolyte as described above,
It can be configured similarly to a conventional lithium ion secondary battery.

That is, as the negative electrode material, a material capable of inserting and extracting lithium can be used. A constituent material of such a negative electrode, for example, a non-graphitizable carbon-based material or a graphite-based carbon material can be used. More specifically, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke), graphites, glassy carbons, and organic polymer compound fired bodies (phenolic resin, furan resin, etc.) at an appropriate temperature Carbon materials such as fired and carbonized), carbon fiber, and activated carbon can be used. In addition, as a material capable of inserting and extracting lithium, a polymer such as polyacetylene and polypyrrole and an oxide such as SnO ₂ can be used. When forming the negative electrode from such a material, a known binder or the like can be added.

The positive electrode depends on the type of the intended battery.
Metal oxide, metal sulfide or specific polymer as positive electrode active material
It can be used as a quality. For example, Lichiu
When constructing a M-ion battery, T
iS₂, MoS₂, NbSe ₂, V₂O₅Etc. lithium
Containing no metal sulfide or oxide, Li_xMO
₂(Where M represents one or more transition metals, and x represents the charge of the battery.
Depends on discharge state, usually 0.05 or more and 1.10 or less
Below. Uses lithium composite oxides mainly composed of
can do. Construct this lithium composite oxide
As the transition metal M, Co, Ni, Mn and the like are preferable.
A specific example of such a lithium composite oxide is LiC
oO₂, LiNiO₂, LiNi_yCo_1-yO₂(formula
Where 0 <y <1. ), LiMn₂O₄Etc.
be able to. These lithium composite oxides require high voltage
A positive electrode active material that can be generated and has excellent energy density
Become. For the positive electrode, several types of these positive electrode active materials are combined.
May be used. In addition, using the positive electrode active material described above
When forming a positive electrode by using, known conductive agents and binders
Etc. can be added.

As the film-like outer case 3, an aluminum laminate film or the like in which nylon, aluminum and polypropylene are laminated in this order is used.

The electrode terminals (positive terminal lead 4 and negative terminal lead 5) are joined to the current collectors of the positive and negative electrodes, respectively. Is desirable. For the negative electrode, copper, nickel, or an alloy thereof can be used.

The solid electrolyte secondary battery 1 configured as described above is manufactured as follows.

First, an assembling process for preparing a battery precursor in which a positive electrode and a negative electrode capable of inserting and extracting lithium and a solid electrolyte are packaged in a layered film-like package case 3 is performed.

In the assembly process for producing the battery precursor,
First, a positive electrode is manufactured. A positive electrode mixture is prepared by mixing a positive electrode material capable of inserting and extracting lithium with a binder, a conductive agent, and the like,
This positive electrode mixture is dispersed in a solvent to form a slurry. Next, a slurry-like positive electrode mixture is applied to both surfaces of the positive electrode current collector, dried, and then compression-molded at a constant pressure to obtain a belt-like positive electrode.

Next, a negative electrode is manufactured. A negative electrode mixture is prepared by mixing a negative electrode material capable of inserting and extracting lithium and a binder, and the negative electrode mixture is dispersed in a solvent to form a slurry. Next, a slurry-like negative electrode mixture is applied to both surfaces of the negative electrode current collector, dried, and then compression-molded at a constant pressure to obtain a belt-like negative electrode.

Next, a gel electrolyte solution is prepared by mixing a non-aqueous solvent, a plasticizer containing an electrolyte salt, a polymer material, and a solvent, and the gel electrolyte solution is formed on the active material layers of the positive electrode and the negative electrode. Is uniformly applied, impregnated, heated or reduced in pressure, and the solvent is evaporated and removed to solidify. In this way, a gel electrolyte which is impregnated and solidified is formed on the active material layers of the positive electrode and the negative electrode. When a crosslinked gel electrolyte is formed, it is solidified by crosslinking with light or heat.

Next, the positive electrode and the negative electrode are laminated via the gel electrolyte and wound in the longitudinal direction to form a wound battery element 2. Next, the wound battery element 2 is packaged with a layered film package case 3. Thus, a battery precursor is produced.

After the assembling step of manufacturing the battery precursor, an initial charging step is performed for the battery precursor to perform an initial charging at an environmental temperature of 15 ° C. or more and 50 ° C. or less.

Originally, the environmental temperature at the time of initial charging of the battery precursor was room temperature. However, room temperature
It fluctuates depending on the season, time, weather, etc. and is not constant. For this reason, in the solid electrolyte secondary battery initially charged at room temperature, the battery capacity fluctuates according to the change in room temperature.

On the other hand, in the method for manufacturing the solid electrolyte secondary battery 1 to which the present invention is applied, the temperature environment at the time of the first charge is controlled within a certain range. Later variations in battery capacity are prevented.

In the initial charging step, it is appropriate to first charge the battery precursor at an environmental temperature of 30 ° C. or more and 50 ° C. or less, and an environmental temperature of 30 ° C. or more and 35 ° C. or less It is optimal to perform the first charging within the range of. When the temperature environment at the time of the first charge is set to a temperature range of 30 ° C. or more and 50 ° C. or less, which is a temperature range of room temperature or more, and more preferably a temperature range of 30 ° C. or more and 35 ° C. or less, Variation is prevented and the internal resistance of the solid electrolyte is further reduced, so that the discharge capacity per cycle increases.

In the first charging step, the environmental temperature
If the temperature exceeds 0 ° C., the non-aqueous electrolyte contained in the gel electrolyte is decomposed and gas is generated in the film-shaped outer case 3, so that the outer shape of the solid electrolyte secondary battery 1 may be deformed. is there.

According to the method for manufacturing a solid electrolyte configured as described above, variation in battery capacity after initial charging is prevented, and a solid electrolyte secondary battery 1 with stable quality can be manufactured. In particular, in the first charging step, the ambient temperature is 15 ° C. or higher,
By performing the first charging in the range of 50 ° C. or less, preferably in the range of 30 ° C. or more and 50 ° C. or less, more preferably in the range of 30 ° C. or more and 35 ° C. or less, the capacity is increased and the quality is stabilized. The solid electrolyte secondary battery 1 can be manufactured.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a solid electrolyte secondary battery to which the present invention is applied will be described in detail based on specific experimental results.

Sample 1 [Preparation Method of Positive Electrode] A suspension of the following positive electrode active material layer composition was mixed by a disper for 4 hours, and this was pattern-coated on both sides of a 20 μm-thick aluminum foil. Coating pattern, coating length 160mm on both sides, uncoated portion length 30mm
, The positions of the start and end of coating on both sides were controlled so as to coincide with each other.

<Positive Electrode Active Material Layer Composition> LiCoO ₂ 100 parts by weight Polyvinylidene fluoride (average molecular weight 300,000) 5 parts by weight Carbon black (average particle diameter 15 nm) 10 parts by weight N-methyl-2-pyrrolidone 100 parts by weight LiCoO ₂ has an average particle size of 10 μm, a minimum particle size of 5 μm, a maximum particle size of 18 μm, and a specific surface area of 0.25 m.
² / g.

Next, the raw material of the positive electrode after both-side coating was applied at a linear pressure of 30%.
Pressed at 0 kg / cm. The positive electrode thickness and the positive electrode active material layer density were 100 μm and 3.
It was 4 g / cc.

[Preparation Method of Negative Electrode] A suspension of the following negative electrode active material layer composition was mixed by a disper for 4 hours, and this was pattern-coated on both sides of a 10 μm thick copper foil.

<Negative Electrode Active Material Layer Composition> Artificial graphite (average particle size: 20 μm) 100 parts by weight Polyvinylidene fluoride (average molecular weight: 300,000) 15 parts by weight N-methyl-2-pyrrolidone 200 parts by weight The negative electrode substrate is subjected to a linear pressure of 300 kg / cm.
Pressed. The negative electrode thickness and the positive electrode active material layer density were 90 μm and 1.30 g / cc after pressing, respectively.

[Preparation Method of Electrolyte-Containing Gel Layer-Forming Composition] The electrolytic solution-containing gel layer-forming composition was prepared by mixing with a disper under heating at 70 ° C. for 1 hour.

<Composition for Forming Electrolyte-Containing Gel Layer> Poly (hexafluoropropylene-vinylidene fluoride) copolymer 5 parts by weight Dimethyl carbonate (DMC) 75 parts by weight Electrolyte solution (LiPF ₆ : 1 mol / l) 20 parts by weight Part In poly (hexafluoropropylene-vinylidene fluoride), the content of hexafluoropropylene is 6 parts. In preparing the electrolytic solution, a non-aqueous solvent in which ethylene carbonate and propylene carbonate were mixed at a ratio of 4: 1 was used.

[Method of Manufacturing Battery] First, the gel composition for forming an electrolyte solution-containing gel prepared as described above was applied to a layer having a thickness of 20%.
A pattern was applied to the negative electrode active material layers on both sides of the negative electrode so as to have a thickness of μm. At this time, the dryer was prepared so that substantially only dimethyl carbonate was evaporated. The positive electrode and the negative electrode were heated by setting the electrode preheating device to a predetermined temperature (60 ° C.) when forming the electrolyte-containing gel layer.

Next, the negative electrode raw material on which the electrolyte-containing gel layer was formed was cut into a width of 40 mm to prepare a pancake of a strip electrode. Then, the positive electrode raw material was cut into a width of 38 mm to produce a pancake of a strip-shaped electrode.

Thereafter, a lead wire was welded to each of the positive and negative electrodes, and the electrodes were bonded so that their electrode active material layer surfaces face each other, pressed, and sent to a built-in portion to form a battery element.

Then, the battery element was sandwiched so as to be covered with the laminate film, thereby producing a precursor of the solid electrolyte secondary battery. In addition, as the laminated film, nylon having a thickness of 30 μm and thickness of 40
A layer in which aluminum having a thickness of 30 μm and unstretched polypropylene (CPP) having a thickness of 30 μm were sequentially laminated was used.

Next, with respect to the battery precursor, an ambient temperature of 20
C. and the first charge was performed. As the initial charging method, constant current charging is performed by a constant current control of a charging current value of 0.5 A until the battery voltage becomes 4.2 V, and subsequently, a constant current control of 4.2 V is performed and the charging current value is reduced. Charging was performed until the current reached 0.01 A.

Samples 2 to 6 A solid electrolyte secondary battery was prepared in the same manner as in Sample 1, except that when the battery precursors were initially charged, the environmental temperatures were as shown in Table 1 below.

The first-charged samples 1 to 6 prepared as described above were discharged at a constant current of 0.2 A until the battery voltage reached 3.0 V, and the initial discharge capacity was measured. At this time, the environmental temperature in the discharge equipment was 23 ° C., which is room temperature.

Also, 0.2C of sample 1 to sample 6
The capacity, the 1C capacity and the 3C capacity were measured, and the capacity retention after 200 cycles was measured. As a method for measuring the capacity retention ratio, first, at room temperature, constant-current constant-voltage charging was performed under the conditions of an upper limit voltage of 4.2 V, a current of 0.5 A, and 3 hours, and then a constant-current discharge of 0.5 A was terminated. The operation was performed up to a voltage of 3.0 V. Performing 200 such charge / discharge cycles,
200 when the discharge capacity at the first cycle is 100%
The discharge capacity at the cycle was calculated and defined as the capacity retention rate.

Table 1 shows the results of the above measurements.

[0055]

[Table 1]

With reference to Sample 1 in which the environmental temperature at the time of the first charge was 20 ° C., the environmental temperature of the first heavy electromagnetic was 60 ° C.
It can be seen from Table 1 that Sample 6 having the capacity retention ratio at the 200th cycle was lower than that of Sample 1 and the battery performance was deteriorated. That is, it can be said that the quality of the sample 6 is unstable.

Further, when the discharge is performed by changing the degree of the load by changing the discharge current, the environmental temperature at the time of the first charge is 30 ° C. to 50 ° C., regardless of whether the load is light or heavy. Sample 2 to Sample 5 in the range of ° C
It can be seen that, compared to Sample 1, a better discharge capacity was achieved. In particular, in the case of heavy load, sample 2
Sample 5 is compared with Sample 1 and Sample 6,
The capacity has increased by about 5 to 8%.

Therefore, the environmental temperature at the time of the first charge is set to 15
It can be seen that a solid electrolyte secondary battery with stable quality can be obtained by performing the process in the range of not less than 50 ° C. and not less than 50 ° C.
Further, the environmental temperature at the time of the first charge is in the range of 30 ° C. or more and 50 ° C. or less, and more preferably, the environmental temperature at the time of the first charge is 3 ° C.
It is understood that when the temperature is in the range of 0 ° C. or more and 35 ° C. or less, variation in battery capacity is prevented, and a solid electrolyte secondary battery with stable quality can be obtained.

[0059]

As is apparent from the above description, according to the method for manufacturing a solid electrolyte battery according to the present invention, the positive and negative electrodes capable of inserting and extracting lithium and the solid electrolyte are packaged in a film-shaped package case. After assembling to produce a battery precursor comprising:
Since the first charge is performed by controlling the temperature in a fixed range of not less than 50 ° C. and not less than 50 ° C., variation in the battery capacity after the first charge is prevented. Therefore, according to the method for manufacturing a solid electrolyte battery according to the present invention, a solid electrolyte battery having stable quality can be manufactured.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a configuration example of a solid electrolyte secondary battery.

FIG. 2 is a perspective view illustrating a configuration example of a solid electrolyte secondary battery.

[Explanation of symbols]

1 solid electrolyte battery, 2 battery element, 3 film outer case

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H029 AJ14 AK02 AK03 AK05 AK16 AL02 AL06 AL07 AL08 AL16 AM00 AM07 AM11 AM16 BJ04 CJ16 CJ28 DJ02 HJ14

Claims (4)

[Claims] 1. An assembling step of preparing a battery precursor in which a positive electrode and a negative electrode capable of inserting and extracting lithium and a solid electrolyte are packaged in a film-shaped package case, and an ambient temperature of 15 ° C. Above, 50 ℃
A method for producing a solid electrolyte battery, comprising: an initial charging step of performing first charging within the following range. 2. The method for producing a solid electrolyte battery according to claim 1, wherein in the first charging step, the battery precursor is first charged at an ambient temperature of 30 ° C. or more and 50 ° C. or less. 3. The method for producing a solid electrolyte battery according to claim 2, wherein in the initial charging step, the battery precursor is first charged at an ambient temperature of 30 ° C. or more and 35 ° C. or less. 4. The method according to claim 1, wherein the solid electrolyte is a gel electrolyte composed of an electrolyte salt, a non-aqueous solvent, and a matrix polymer.